Breast cancer surgery in the U.S. exhibits little regionalization, with a large number of low volume providers. Several studies now show that higher surgeon volume of cases is associated with better 5-year survival. These studies suggest that the patients of surgeons performing at least 15-30 breast cancer operations annually have a 25% lower risk of all cause mortality. While these findings are important, the surgeon volume-outcome relationship requires further investigation before major policy initiatives are proposed. The possible contribution of selection bias to the observed relationship requires more study. Higher volume surgeons care for patients of higher socioeconomic status, the effect of which has been controlled for only ecologically. Disease recurrence, an outcome less subject to bias than is all-cause mortality, has not been studied. There is little understanding of what processes of care contribute to the volume-outcome association. This proposal aims: Specific Aim 1. To examine the relationship of surgeon volume and the 5-year outcomes of overall mortality and disease recurrence among women undergoing incident breast cancer surgery, controlling for age, ethnicity and race, patient-level SES and insurance coverage, extent of disease, and comorbidity. Specific Aim 2. To examine the effectiveness and cost-effectiveness of long-term hormonal adjuvant therapy (e.g. tamoxifen) among a population-based sample of older women with incident breast cancer, as well as the extent to which hormonal therapy accounts for any observed surgeon volume-outcome relationship. Specific Aim 3. To examine variations in care received by older women undergoing incident breast cancer surgery, and to examine the relationship between multiple initial processes of care and outcomes (death, recurrent disease, quality of life, functional status) at 18, 30, 48, and 60 months. Specific Aim 4. To describe the relationship between cost of alternative initial processes of breast cancer care and outcomes among older women, as well as the implications of these relationships for policy initiatives. These aims will be accomplished by studying a population-based sample of older women with incident breast cancer including measures derived from Medicare files, patient survey, and tumor registry data. The results will be critical to informing policy initiatives, including determination of how to best reduce socioeconomic disparities in breast cancer outcomes.